Natural insulation materials

Natural insulation materials such as hemp, sheep’s wool and fl ax are becoming widely recognised for their sustainability. A growing concern for the environment, alongside a need to reduce the energy consumption of built stock, has resulted in a fl ourishing market for these materials.

For many years cellular, oil-based insulation materials have been the most common choice in construction projects. As a growing awareness of the effects of these materials on the environment is being recognised, many architects are making moves to specify natural materials wherever possible.

Natural insulation materials often require a greater thickness of insulation in comparison with standard materials in order to achieve the same U-values. This has commonly been stated as a barrier to their use. A greater understanding of their additional benefits is beginning to reduce these perceived obstacles.

Increasingly, thermal performance is not the only consideration when choosing insulation. Many natural materials also have the added benefits of being breathable, improving internal air quality and reducing condensation levels. As airtight levels improve through requirements in building regulations and the increased use of Passivhaus standards, toxicity and air quality are of greater concern.

The three main types of natural material products are sheep’s wool, cellulose and hemp. Sheep’s wool has been around for a while but its increased availability and use has caused costs to come down. Due to the hygroscopic nature of wool, the insulation is able to absorb, store and release moisture, naturally controlling condensation levels within the building and improving internal air quality.

Cellulose insulation, made from recycled newspaper, is an obvious sustainable choice. It is most commonly used in roof and wall cavities, where it can be pumped and sprayed in.

Hemp has seen a revival as an insulation material. A versatile and fast-growing agricultural crop, it can be used by farmers as part of a crop rotation to condition soil and is becoming more commonly grown in the UK. Acting as a carbon sink, hemp locks in up to 2 tonnes of CO2 per tonne of fibre, making it a particularly sustainable choice. It is available in a variety of different insulation forms. Semi-rigid batts are good for vertical installations as they do not slump, ensuring thermal properties remain constant throughout the wall. Hemcrete, used at Pat Borer and David Lea’s building for the Wales Institute for Sustainable Education at the Centre for Alternative Technology, provides a solid-wall solution, with the advantage of increased thermal mass.

Sheep’s wool insulation

Black Mountain Sheep’s Wool insulation

Due to the hygroscopic nature of the sheep’s wool, this insulation can naturally control condensation levels within the building. The insulation can absorb more than 35 per cent of its weight in moisture without affecting the thermal performance.

Hemp insulation

Black Mountain Hemp insulation

The hemp fibres used in Black Mountain’s insulation are derived from waste straw left behind at the end of the hemp-seed harvest. This use of agricultural bi-products makes hemp insulation a highly sustainable material for use in construction.

Thermafleece Ecoroll

Thermafleece Ecoroll

This wool insulation comes in roll form. Compressed packed, it saves storage space both on site and in transportation. The manufacturers claim it reducestransport impacts by up to 50 per cent compared with other natural insulations.

Warmcel

Warmcel

Warmcel is a full-fill insulation, which can be spray installed ensuring it fills all cavities and spaces around pipework and wiring to provide high levels of thermal performance. This also enhances the airtightness levels that can be achieved.

STEICOflex

STEICOflex

The raw material for STEICOflex comes from thinnings of surrounding pine forests and from saw-mill residue. The flexible insulation board has a water vapour open structure so vapour can pass through to the ventilated cavity, creating a breathable wall construction.

NBT Pavaflex

NBT Pavaflex

The high density of Pavaflex wood-fibre batts means they are self-supporting and do not slump. This high density also allows a level of thermal mass, which provides insulation against summertime overheating.

Tradical Hemcrete

Tradical Hemcrete

Hemcrete is a bio-composite building material made from a combination of hemp shiv and a lime-based binder. Hemcrete is usually cast in-situ around a timber frame to form the walls of buildings, but is also particularly well suited to refurbishment projects.

Isovlas

Isovlas

Isovlas is a flax-based insulation designed for use in timber frame, partitions, lofts, roofs and floors. The high specific heat capacity of the insulation helps to keep the building warm during the winter but cool in summer, preventing overheating.

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